A liquid crystal display is one of numerous types of flat panel displays that are being widely used. A typical liquid crystal display includes two display panels having corresponding electric field generating electrodes such as pixel electrodes and a common electrode formed thereon, and a liquid crystal layer interposed therebetween. When a voltage is applied to the electric field generating electrodes, an electric field is generated in the liquid crystal layer. The electric field determines the alignment of liquid crystal molecules of the liquid crystal layer, which controls the polarization of incident light. In this way, images are displayed.
The liquid crystal display further includes switching elements connected to individual pixel electrodes, and a plurality of signal lines such as gate lines and data lines for controlling the switching elements to apply a voltage to the pixel electrodes.
Among the various types of liquid crystal displays, a longitudinally-aligned-mode liquid crystal display is popular because it has a high contrast ratio and a wide reference viewing angle. In the longitudinally-aligned-mode liquid crystal display, when no electric field is applied, the major axis of each liquid crystal molecule is aligned to be longitudinal to a display panel.
Specific methods of realizing a wide viewing angle in the longitudinally-aligned-mode liquid crystal display include a method of forming cutouts in electric field generating electrodes and a method of forming protrusions on electric field generating electrodes. The cutouts and the protrusions determine the tilt directions of the liquid crystal molecules. Therefore, when the cutouts and the protrusions are suitably disposed so as to disperse the tilt directions of the liquid crystal molecules in various directions, it is possible to achieve the wide reference viewing angle.
In such a liquid crystal display, in order to raise luminance, the strength of the electric field formed in the liquid crystal layer may be increased. However, when an applied voltage to the pixel electrodes is raised in order to increase the strength of the electric field, the electric field formed between the pixel electrodes and the data lines for transmitting the voltage to be applied to the pixel electrodes also becomes stronger. This strong electric field disorders the alignment of the liquid crystal molecules positioned around the pixel electrode edges, increasing the response time of the liquid crystal.
Meanwhile, since it is difficult for light to pass through portions where the protrusions or the cutouts exist, the more protrusions or cutouts, the lower the aperture ratio. However, when the separation between the protrusions or the cutouts increases in order to raise the aperture ratio, the effects of the protrusions or the cutouts are relatively decreased and disturbance in the electric field due to the data lines becomes severe, thus increasing the response time.
In a rectangular liquid crystal display in which pixel electrodes are parallel with gate lines and data lines, an electric field generated between neighboring pixel electrodes disorders the alignment of liquid crystal molecules. As a result, a texture is generated. Accordingly, the transmittance is decreased and a residual image remains on a screen.
In order to reduce such texture, a cutout of a common electrode may overlap a side of a pixel electrode. However, the aperture ratio may be lowered, which may have the undesirable effect of reducing transmittance.